The FDA can crack down on false marketing, but by law it's not allowed to oversee the manufacture/testing of supplements, so that leaves it with few teeth to do anything but wrist-slap egregious marketing. My view is the FDA should be granted full authority to oversee supplements, but that would mean a significant budget boost that may not go over so well in Washington. Here's the agency's FAQ on this, which I've now linked to within the story too (so: thank you for asking!): https://www.fda.gov/food/information-consumers-using-dietary-supplements/questions-and-answers-dietary-supplements